Ideas on this misfire?

Jacob · Apr 18, 2018

It's very hard to explain -- or even hear now as I just recently put my flowmaster 60 delta on. It was very easy to hear without the muffler.

I had originally thought that it was in part of the alternator voltage regulator failing - which I assume is from a power steering leak that sprang up. All is good with that now and I put a desk alternator in.

In the video I set my baseline as 2000 rpm and you can see how it'll drop then surge a few seconds later. During the video I didn't change my footing too much and it sorta feels like the throttle becomes non-existent then jerks back in much like an aged AT from this era.

The power loss happens throughout nearly all rpm bands but mostly your standard town/city driving. Most of the time forcing a downshift with wot will work but you can feel a difference - sometimes I don't hear vtec hit. Definitely can't feel vtec if you romp it when losing power.

Car has 266k
12k miles ago (about 16 months) had a JDM F23a stuffed into it. Supposed to be 60-70k miles when I got it. Auto transmission original - has the 2nd clutch pressure switch issue but still it rather healthy condition.

I've changed the alternator, resealed power steering pump, cleaned iat, replaced pcv valve, checked air filter and the cleaner/resonator chamber and plugs seem good. Coming up I am checking/changing distributor, and doing fuel pressure test soon. I'm hoping someone has seen a similar issue and can help me figure this out real soon.

Thanks guys!

https://youtu.be/yQG6sf6zPS8

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Jacob · Jan 5, 2019

I forgot I had even posted this but the problem ended up being upstream o2 sensor.

Granted it wasn't a Honda or sensor, it still worked the same.

I believe what happened to it was running cleaner in the gas tank then after a few weeks seafom thru brake booster vacuum line.

Since the intake has the factory manifold it's probably real dirty and i doubt the mechanics cleaned it up. All that I think may shot through and wrecked the O2 sensor.

I read the sensors with multi meter and obd2 reader as well as dry wiped em before reinstalling as part of my previous testing. The o2 sensors always read find but my fuel trims were kinda wild. I can't remember exact figures but I think I have a picture somewhere: long term I think got to -20 and of course the short-term was all over the place +/-20

I disconnected the O2 sensor and did my thing for 2 days(less than 25) miles. During that time my car was in limp mode but never misfired. After work that 2nd day I plugged it back up and drove straight to the junkyard. Of course it started doing it's intermittent misfire crap again.

It cost me $1.99 on junkyard credit. Had the battery disconnected while in the yard, swapped it out and drove home. The car relearned idle and has felt brand new since.

On that note though I did see just once a catalyst below efficiency where downstream pegged at 1.2v. I have a cheap eBay hi flow cat with the same sensor type as upstream. I can kinda hear it in my exhaust and know that cat is junk but I'm thinking that sensor got wrecked from the same thing.

Sorry it took so long to respond my solution guys.

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